Telescopic feed leg for hydraulic tools



J. E. FEUcHT r-:TAL 955,572 TELEscoPIc FEED LEG FOR HYDRAULIC TooLs Filed Jan. s1, 195e Oct. 11, 1960 2 Sheets-Sheet 1 i NU 3 l Wh" II'I'MI'I4 5 v 23 22 INVENTORS 40 JAcoB E. FEucHT 42 ALBERT FEucHT Oct. 11, 1960 J. E. FEUCHT Erm.

TELEscoPIc FEED LEG FOR HYDRAULIC TooLs 2 Sheets-Sheet 2 Filed Jan. 31. 1958 INVENTORS JACOB E. FEUCHT ALBERT FEUCHT 'orneys United States Patent lce '.mLEscoPIc FEED LEG non HYDRAULIC TooLs Filed Jan. 31, 1958, Ser. No. 712,366

Claims. (Cl. 121-9) This invention `relates generally to expansible fluid chamber devices and more particularly to telescopic motors for exerting feeding pressures on drills, jacks and similar mechanisms. The invention finds particular utility in feeding rock drills in vertical hole drilling operations in confined spaces that vary in height from one place to another. Y

For example, in drilling roof bolt holes in coal mines, the roof height may vary from one location to another, and it is desirable to have a tool of minimum collapsed height so as to require as few drill steel changes as possible.

Telescopic feed drills have been proposed which afford a relatively short collapsed height and which have a considerable feed travel. These prior art devices, however, have been rather complicated, contain numerous parts which are costly to produce and maintain and which are diflicult and time consuming to disassemble in order to replace certain parts, such as fluid seals.

Many of these prior art devices provide unequal feeding pressure during the total expansion stroke of the various piston elements. Another short coming of some prior art devices is the short life of some of the mating surfaces, particularly bushings, due to localized wear caused by vibration during the drilling cycle. This wear is aggravated by the fact that as the feed leg extends, its various sections have increasingly less lateral stability relative to one another.

It is a general object of the present invention to overcome the above mentioned difculties.

According to the present invention, a telescopic feed stantially uniform -feeding force vthroughout its entire feed stroke.

The invention further provides a tool of the above type having means for centralizing the telescoping parts relative to one another which substantially increases the stability therebetween. As a result localized wear has been minimized with a marked increase in parts life'.

The tool feed means provided in accordance with the invention permits ready servicing and maintenance of the tool and, in particular, facilitates the disassembly of the feed means when it is desired, for example, to replace the packings thereof.

These -and other objects and advantages will appear hereinafter as this disclosure progresses, reference being had t-o the accompanying drawings, in which:

Figure l isan elevational View of a hydraulic tool and showing in section a telescopic feed device made in accordance with the present invention;

Figure 2 is `a sectional view of the feed device shown in Figure l, with the intermediate and end pistons ex-` tended from the outer cylinder, and Y Figure 3 is a view similar to Figure 2 and shows the feed device in the fully extended position. A The invention will be described `as being applied to a pneumatic tool, although Vthe invention contemplates the use of other uids, such as oil.

vhas been provided for a pneumatic tool which has subing bushing 22 or 40.

' Patented Oct. 11, 1960 Referring in greater detail to the drawings, the pneumatically operated rock drill 9 has a drill steel 10 and is connected to the `front head bracket 11 and backhead bracket 12 of the pneumatically actuated telescoping feed leg 13. p

The feed `mechanism 13 includes the outer cylinder 14 which is threadably engaged'in the backhe-ad 15. Compressed air is ported into cylinder 14 by the valve 16 which is in communication with the air supply source (not shown). Air is admitted to the cylinder from the valve via port 17 in the backhead and into the cylinder chamber 18. Chamber 18 is formed between the cylinder 14 and the center balancing hollow rod 20 which is also threadably engaged in the backhead 15.

A bushing 22 is threaded in the end of cylinder 14 and has an outwardly converging taper 23.

An intermediate piston 25 forms a close sliding fit with the internal diameter of bushing 22 for reciprocation therein. Piston 25 has a head 26 threaded on its end, which head has an external circumferential surface 27 that forms a close sliding t with the internal surface 28 of the outer cylinder 14. The piston head ,packing 29 is of the rubber V-shaped type and seals against the cylinder surface 28. v The piston head 26 has a tapered surface 30 which is complementary to taper 23 and nests tightly therein when intermediate piston 25 is extended as shown in Figures 2 and 3. By means of these complementary tapered surfaces on the intermediate piston head and outer cylinder, the head is positively centered in the bore of the cylinder throughout the travel of the end piston 32, as will presently appear. Experience has shown a marked increase in the wear life of these parts as a result of this construction, primarily because localized excess wear due to vibration during the drilling operation has been eliminated. The intermediate piston head 26 has a bore 33 which is larger than the diameter of the center balancing tube 20 and forms an annular port 34 therebetween for passage of fluid from chamber 18 into the intermediate piston. It should be noted the center balancing tube 20 has no projecting heads or other obstructions which facilitates the assembly or disassembly of the unit. This simple :design also contributes to a unit that is economical to manufacture. 4 l The primary purpose of the balancing tube 20 is to port air into the end piston at the proper time in order to effect a balanced pressure throughout the feed range, as will appear. p

The end of the center tube 20 has an annular port 35 milled therein which serves to admit air into the end piston. When this occurs, the pressure is effective on the entire area of the end piston. The end piston 32 has a head 36 threaded on itsV inner end. An external taper 37 is formed on the head which is complementary to the internal taper 43 on the intermediate piston head. Packings 38, 39 are ofthe U-shaped rubber type and slidingly seal against the internal surface of piston 25 and the external surface of the balancing tube 20, respectively. ,Y A bushing 401 is threaded on the end of the intermediate piston 25 and serves to limit Athe outward extension of the end piston by means of its shoulder 41.

The point 42 is threaded on the outer end of the endpiston and has `good wearing characteristics.` '-.j- The rubber U-shaped seals 29, 38 and 39 permit the use of piston heads of simple construction.x To vreplace these seals, it is only necessary to remove the correspond- Another advantageous lmaintenance feature of the present invention is the fact that 3 the bushings 22 and 40 and point 42 are all nested together which permits them all to be made from similar good wearing material, such as hardened or chrome plated steel.

'Operation Y At theibeginni-ng of a drilling operation, the feed leg would be in the collapsed position shown in Figure 1 and the rdrill steel 10 and point 42 adjacent lopposite sides of a tunnel or the like. Air is admitted by valve 16 to the chamber 18 and simultaneously moves both of the pistons 25 and 32 outwardly of the cylinder 14 as the drill steel makes its cut. Because of 'the effective differential pressure area of vthe intermediate piston head and the end piston head, the resultant force holds the end piston head centralized by means of tapers 43 and 37, tightly on the head 26. By forming an accurate and good bearing surface between the pistons, localized wear in piston heads is prevented.

When the intermediate piston 25 reaches its outermost position shown in Figure 2, the tapered surface 30 seats tightly on the complementary surface 23, stopping further extension of piston 25 and centering it in the outer cylinder. At the same time or slightly before intermediate piston 2S reaches its outermost position, the sealing lip of packing 39 will pass porting 35 on balancing tube 20 to admit actuating fluid to become effective on entire surface 44 of small piston tube head 36 and the small piston LD., causing it to move outwardly relative to the intermediate piston 2S. The end piston may then extend until stopped by shoulder 41.

The area within the circumference of packing 38 defines the effective area upon which pressure acts during the last part of the feed leg extension, that is, the travel of the end piston relative to the intermediate piston. This area is identified in Fig. 3 by the arrow line A.

The area which is effective to move both pistons during the initial feed of the unit is defined by the cross sectional area of the inside of the cylinder 14 minus the cross sectional area of the outside dimension of the balancing tube 2i). This effective area is the annulus formed between the cylinder bore and the rod 20, which is identied in Fig. 3 by the arrow lines B.

Areas A and B are substantially equal and a balanced feeding force is therefore effective n the unit for the entire length of its feeding travel.

To collapse the feed leg, valve 16 is vented to atmosphere and a spring tension ring 45 engages the bore of point 42, as shown in Fig. l to hold the leg in the collapsed position to prevent accidental extension thereof. In order to be able t-o quickly and completely retract the telescopic members within one another, means must be provided to permit the air within the end piston to readily escape to the atmosphere. For example, in the last phase of retraction when the small end piston engages on the center balancing tube, a passage must be provided between the interior of the end piston and the chamber 18. However, this passage must be ineffective during the expansion stroke. For this purpose, a passage 47 is drilled in the plug 48. A one-way check valve 50 permits air pressure to ow from the end piston into the interior of the center tube and then out port '51 to atmosphere. The check valve shown is of the reed type but of course other forms may be used, such as ball checks, gate checks or the like. Furthermore, the check valve may be located at the other end of lthe center balancing tube for forming the one-way passage to the chamber 18.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and Ydistinctly claiming the Vsubject matter which is regarded as the invention.

We claim:

.1. In combination, an outer cylinder having a bushing threaded on one end and a closed backhead on its other end, a center rod concentrically disposed in said cylinder and secured at one end within said cylinder, said rod having a fluid portpadjacent its free end, said bushing having an internal tapered surface, an intermediate piston reciprocable in said bushing and having a head for reciprocation in said cylinder and scalable therewith, said intermediate piston and head adapted to telescope over said rod, said head having an external tapered surface Which -is complementary said internal tapered surface and engageable therewith when said piston -is ful-ly extended so as -to Ycenter the latter in said cylinder, said head also vhaving an internal taper, said intermediate piston having a bore extending therethrough, an end piston closed at one end and having a head at its other end Which is reciprocable in said intermediate piston and is scalable therewith, said end piston and head having a bore extending therethrough so as to telescope over said rod when in the collapsed position, said end ypiston head sealingly engageable on said rod during movement of said intermediate piston over said rod, said end piston head having an external taper on the end thereof which is complementary to said intermediate piston head internal taper and adapted to center firmly thereon when said end piston is fully contracted into said intermediate piston.

2. A telescopic feed leg for a drill comprising, an outer cylinder hav-ing a bushing threaded on one end and a closed backhead on its other end, a center rod concentrically Adisposed'in said cylinder and secured at one end within said cylinder, an intermediate piston reciprocable in said bushing and having a head for reciprocation in said cylinder and scalable therewith, said intermediate piston and head adapted to telescope over said rod, said rod and intermediate piston defining a first expansible chamber, an end piston closed at one end and having a head at its other end which is reciprocable in said intermediate piston and `is scalable therewith, said end piston and head having a bore extending therethrough so as to telescope over said rod when in the collapsed position, said end piston head sealingly engageable on said rod during movement of said intermediate piston over said rod, and a bleed passageway including a one-way check valve from said end piston bore to said first chamber whereby said feed leg may collapse completely.

3. A telescopic feed leg for a drill comprising, an outer cylinder having a backhead secured at one end, a cen- -tral .rod fixed to said backhead and extending into said cylinder, a hollow intermediate piston reciprocable in said cylinder and around said rod, said rod and intermediate piston defining an expansion chamber, an end piston having a closed end and reciprocable in said intermediae piston and scalable around said rod, the effective pressure `area acting on said intermediate piston defined by `said cylinder and said rod, whereby said end piston moves With `said intermediate piston as a unit during an initial extension phase until said intermediate piston is fully extended and said end piston is unsealed from said rod, and then said end piston moves by itself during a second extension phase to a fully extended position, and a bleed passageway including a one-way check valve from the interior of said end piston to said chamber whereby said feed leg may be completely retracted.

4. In a fluid actuated telescopic feed leg device, a cylinder having a bore, a backhead at one end of said cylinder, an intermediate piston reciprocally received in said bore and having a smaller bore, a generally hollow second piston reciprocably received in said smaller bore, a central rod in said cylinder and fixed to said backhead, said rod `and intermediate piston cooperating to define an expansion chamber, said rod extending into said pistons when said device is collapsed and of such length so as to be separable from said second piston when said device is fully extended, and a bleed passageway extendin g from the interior of said second piston tosaid chamber and having a one-Way check valve therein whereby said feed leg may be completely collapsed.

5. In a fluid actuated telescopic feed leg device, a cylinder having la bore, a backhead at one end of said cylinder, an intermediate piston reciprocably received in said bore and having -a smaller bore, a generally hollow second piston reciprocably Ireceived in said smaller bore, a central rod in said cylinder and flxed to said backhead, said rod and intermediate piston cooperating to define an expansion chamber, and a bleed passageway extending from the interior of said second piston to said chamber and having a one-way check valve therein whereby said feed leg may be completely collapsed.

References Cited in the le of this patent UNITED STATES PATENTS 2,296,819 Osgood Sept. 22, 1942 2,680,596 Houston June 8, 1954 2,689,547 Pearson Sept. 2l, 1954 10 2,754,804 Miller July 17, 1956 2,804,848 OFarrell et al. Sept. 3, 1957 

